Over the last several years, Dr. C. Alvin Paulsen, Co-Program Director, has been the Coordinator of the World Health Organization Task Force on the Regulation of Male Fertility. In the course of this administrative work, as well as in his own recent research, directed at developing effective contraceptive agents for males, he was confronted with several important unanswered questions. These included: How do we determine the fertilizing capacity of human sperm? What constitutes a normal seminal fluid in men? How does one statistically analyze and describe data from seminal fluid examinations so as to allow meaningful assessment of changes induced by experimental manipulations? What are the limiting factors in the hormonal environment for the maintenance of normal spermatogenesis? These questions are also of central relevance in studies directed toward further understanding of human male infertility, another long term focus of Dr. Paulsen's research and clinical work.